I wouldn’t keep two together regardless of sex. Yea it’s true, a pair of males are more likely to fight over dominance, food, territory, etc, but females are also known to fight over the same things on occasion. You also have to worry about if they’re both getting enough heat and UVB, as the dominate female will probably take the best basking spot, leaving the other to get what it can get. Keeping them together just causes unneeded stress in my opinion, and considering bearded dragons do most of their growing the first year of their life, I think the risks are more than the rewards.
Now, if you’re dead set on keeping two together, keeping two females is way safer than two males, but still that doesn’t prevent any of the issues I mentioned above. End of the day, I wouldn’t recommend cohabitating.